Chemicals, plastics and rubber industries

CO adsorption and reaction on clean and oxygen-covered Au(211) surfaces

Article Abstract:

Temperature-programmed desorption (TPD) and infrared reflection-absorption spectroscopy were used primarily to investigate CO adsorption on a Au(211) stepped single-crystal surface. It was concluded that the presence of the particular step sites at the Au(211) surface imparts stronger CO bonding and a higher reactivity than on the flat Au(111) surface but they are unlikely to provide the reactive sites that are responsible for the remarkable properties for catalysts comprised of small Au nanoparticles on metal oxide supports.

Indications for a surface temperature excess in heterogeneous catalysis

Article Abstract:

A study explored the surface temperature excess (DELTA) = [T.sup.r] -- [T.sup.m] (real reaction temperature [T.sup.r], measured catalyst temperature [T.sup.m]) on the basis of experimental data, a gradually curved Arrhenius plot for CO oxidation reactions over Pd/gamma-[Al.sub.2][O.sub.3] catalysts. Results show that [T.sup.r] in the 2-dimensional reaction surface of an active heterogeneous catalyst is different from [T.sup.m] in the catalyst surface or the temperature [T.sup.g] of the medium.

The excited-state properties of the five-coordinate heme-CO adduct (5cH) as well as the 6c heme-CO adduct (6cH) with a weak axial ligand are studied using time-dependent density functional theory (TD-DFT). The results show that the Q excited state of 6cH-Im crosses the Fe-CO dissociative state (2A') without large elongation of the Fe-CO bond, whereas the Q state of the 5cH does not cross the Fe-CO dissociative state but results in the formation of the excited spin state with a bent Fe-C-O.